Product development and testing of pleated filter media have indicated that pleat spacing is paramount to obtain optimum product performance in some applications, for example, where pleated filter media used in gas turbine cartridge filters. To ensure a low pressure loss across a filter, the entry and exit losses generally need to be minimized, which may be accomplished by maintaining adequate pleat spacing between adjacent pleats to prevent pleat-to-pleat contact (or “breaching”). Some filter media types, such as those that are not pre-corrugated or cannot be processed with an embossed pleat spacing feature, may rely on beads of hotmelt adhesive being applied during the media conversion into pleated form to maintain a uniform spacing. In cartridge style filters, a single grade of hotmelt adhesive is often applied either in a continuous or intermittent bead formation to one surface only of the filter media. Once formed into the cartridge, a spiral melt hotmelt bead or a spacing band may be applied to the outer surface to stabilize the pleats. However, the aforementioned assembly techniques often require manual intervention to evenly space the pleats. Such manual intervention may prove extremely costly and/or time consuming.
Applying adhesive beads to both surfaces of a pleated filter media is acceptable on some filter styles, such as flat panel or vee bank style filters, for example. However, applying adhesive beads to both surfaces of a pleated filter media, and then attempting to form it into a cylindrical or cartridge style filter, may cause strain between the adhesive bead and the filter media, especially at the outer circumference. As the filter media is formed into a cylindrical or conical shape, the strain leaves the filter media susceptible to damage and/or loss of filter integrity. The risk of damage is worsened with an increase in pleat depth.
Thus, there is a need in the art for overcoming the issues of existing systems.